1. Field of the Invention
The present invention generally relates to a reverse flow cooled dynamoelectric machine, and more particularly to an improved arrangement for cooling the end regions of the stator of a reverse flow cooled dynamoelectric machine.
2. Description of the Prior Art
Dynamoelectric machines, such as large turbine-generators, have typically been cooled by a gas such as hydrogen flowing through the interior of the rotor, through the gas gap between the rotor and stator, and through passages between the stator laminations.
However, as the ratings of large turbine-generators increased, it was found that the heating produced in the end regions of the generator rotors became a limiting factor in the capablity of these machines. In order to cool these localized areas of excessive heating in the generator rotors, a reverse flow cooling scheme was adopted wherein cooling gas was pumped by the fan first to a gas cooler, the flow then being divided, a portion of it being pumped into the rotor at an end region thereof to cool the rotor, and the remainder of the gas being pumped through the cooling passages of the stator core.
Such a reverse flow ventilation scheme is described in U.S. Pat. No. 3,739,208 to Shartrand.
However, in such a reverse flow cooling scheme the ventilation loss in the gas gap not only increased, but also effective cooling was not achieved because of the impinging of the gas employed to cool the end portions of the stator with the gas employed to cool the end portions of the rotor.
The end portions, especially at the inner circumference of the stator, are heated due to stray load loss by stray flux from rotor and stator end portions. Therefore, it is a problem to effectively cool the end portion of the inner circumference (i.e. teeth) of the stator.